Hi
This is my first build hope you enjoyed playing with it as much as i do :D

Well you might see already why i have chosen these masteries, though you might not understand why i have chosen ap as well as ad . Well a lot of people play kog'maw full ad but i noticed its much better when you would go hybrid

I have chosen these runes because if you are a spammer :P like me you will be having a lot of mana shortage. I have also chosen armor penetration because if you would use the slow in combo with the bio-arcane in early game you might not hit so much so thats about the armour penetration runes

I have chosen boots of speed for movement speed (Kog'maw is very slow early game without boots and passive also isnt gonna help when you have no movement) and the potions so you can stay in the lane longer. Hopefully when you are going to do your first recall you can buy berserkers graves and amplifying tome ( if ur good buy sheen 2 :P) Sheen is a usefull item because of the bonus you get after using an ability ( you will spam a lot so lot of bonusses). After this buy a phantom dancer, its a good combo of movement speed and attack speed. Hextex gunblade gives attack damage, life steal, ability power and spell vamp its a good item because of the artillery and you will be a lot harder to kill because you gain a lot of health with attacking. after this i said trinity force and frozen mallet , though the frozen mallet is nescesary you can switch them with other items wich will be better of use vs your enemies

you must make good use of the artillery so my advice is before the fight starts fire a few shots but dont spam to much because you will be needing your mana for in a teamfight